Take a ketchup packet from a fast food restaurant, bend it half, poke a few holes in it with a fine needle on the two bulged ends. Then, VERY gently set it under the toilet seat (Needle holes facing forwards) under the nub that contacts the porcelain. Oh, then wait.
Did it to my wife, it works! lol
If that's too technical, just place saran wrap over the toilet bowl making sure there's no wrinkles visible underneath the toilet seat. This is particularly handy for those pesky men whom never lift the seat to go #1.
Paybacks are a b#tch! lol